In a vehicle such as an automobile, in order to improve the thermal efficiency of an internal combustion engine, a supercharger which compresses the outside air and feeds the compressed air to a cylinder may be mounted. As the supercharger, a turbocharger which rotates a turbine by the exhaust of an internal combustion engine to drive a compressor is known. However, in the turbocharger, improvement of turbo lag, improvement of response, or the like is required.
PTL 1 discloses a supercharger including an electric motor. In the supercharger including the electric motor, the improvement of the turbo lag or the response generated in the above-described turbocharger can be expected. However, in the supercharger, vibrations are likely to increase during rotation due to the weight of a rotor of the electric motor. Accordingly, in the supercharger of PTL 1, in order to decrease vibrations, the rotor is rotatably supported on both sides in an axial direction of the electric motor. However, the vibrations of the supercharger increase as a rotation speed of the electric motor increases. Accordingly, there is a case where noise becomes large only by supporting the rotor on both sides in the axial direction of the electric motor.
Therefore, in PTL 1, a sleeve is further provided on the outside in a radial direction of a rolling bearing so as to have a gap between the sleeve and the rolling bearing, and the sleeve is elastically supported from the outside in the radial direction by a damper mechanism. Accordingly, in PTL 1, thermal expansion of the rolling bearing in the radial direction is absorbed by the gap between the rolling bearing and the sleeve, and thus, it is possible to block vibrations of the rotating shaft. Moreover, in the PTL 1, it is possible to prevent transmission of vibrations by the damper mechanism which supports the sleeve.